Air shoe with integrated roller

ABSTRACT

A web-guiding system for guiding a web of media along a transport path including a fixed web-guiding structure and a web-guiding roller. The fixed web-guiding structure includes two sections, each having a pattern of air holes formed through a convex exterior surface. The web-guiding roller is located between the first and second fixed web-guiding structure sections. At least one air source provides an air flow through the air holes in the fixed web-guiding structure sections. The web of media travels around the web-guiding roller and the fixed web-guiding structure through a wrap angle of more than 10 degrees, with the web of media contacting an exterior surface of the web-guiding roller. The air flow through the air holes lifts the web of media away from the first and second web-guiding structure sections.

CROSS REFERENCE TO RELATED APPLICATIONS

Reference is made to commonly assigned, co-pending U.S. patentapplication Ser. No. 14/016,427, entitled “Positive pressure web wrinklereduction system,” by Kasiske Jr., et al.; to commonly assigned,co-pending U.S. patent application Ser. No. ______ (Docket K001680),entitled “Media guiding system using Bernoulli force roller,” by Muir etal.; to commonly assigned, co-pending U.S. patent application Ser. No.______ (Docket K001717), entitled “Wrinkle reduction system usingBernoulli force rollers,” by Muir et al.; to commonly assigned,co-pending U.S. patent application Ser. No. ______ (Docket K001723),entitled “Media diverter system using Bernoulli force rollers,” by Muiret al.; and to commonly assigned, co-pending U.S. patent applicationSer. No. ______ (Docket K001684), entitled “Air shoe with rollerproviding lateral constraint,” by Cornell et al., each of which isincorporated herein by reference.

FIELD OF THE INVENTION

This invention pertains to the field of media transport and moreparticularly to an apparatus for reducing wrinkles while guiding areceiver media web.

BACKGROUND OF THE INVENTION

In a digitally controlled inkjet printing system, a receiver media (alsoreferred to as a print medium) is conveyed past a series of components.The receiver media can be a cut sheet of receiver media or a continuousweb of receiver media. A web or cut sheet transport system physicallymoves the receiver media through the printing system. As the receivermedia moves through the printing system, liquid (e.g., ink) is appliedto the receiver media by one or more printheads through a processcommonly referred to as jetting of the liquid. The jetting of liquidonto the receiver media introduces significant moisture content to thereceiver media, particularly when the system is used to print multiplecolors on a receiver media. Due to the added moisture content, anabsorbent receiver media expands and contracts in a non-isotropicmanner, often with significant hysteresis. The continual change ofdimensional characteristics of the receiver media can adversely affectimage quality. Although drying is used to remove moisture from thereceiver media, drying can also cause changes in the dimensionalcharacteristics of the receiver media that can also adversely affectimage quality.

FIG. 1 illustrates a type of distortion of a receiver media 3 that canoccur during an inkjet printing process. As the receiver media 3 absorbsthe water-based inks applied to it, the receiver media 3 tends toexpand. The receiver media 3 is advanced through the system in anin-track direction 4. The perpendicular direction, within the plane ofthe un-deformed receiver media 3, is commonly referred to as thecross-track direction 7. Typically, as the receiver media 3 expands inthe cross-track direction 7, contact between the receiver media 3 andcontact surface 8 of rollers 2 (or other web guiding components) in theinkjet printing system can produce sufficient friction such that thereceiver media 3 is not free to slide in the cross-track direction 7.This can result in localized buckling of the receiver media 3 away fromthe rollers 2 to create lengthwise flutes 5, also called ripples orwrinkles, in the receiver media 3. Wrinkling of the receiver media 3during the printing process can lead to permanent creases in thereceiver media 3 which adversely affects image quality.

U.S. Pat. No. 3,405,855 to Daly et al., entitled “Paper guide and driveroll assemblies,” discloses a web guiding apparatus having peripheralventing grooves to vent air carried by the underside of the travelingweb.

U.S. Pat. No. 4,322,026 to Young, Jr., entitled “Method and apparatusfor controlling a moving web,” discloses a method for smoothing andguiding a web in which the web is moved in an upward direction pastpressurized fluid discharge manifolds on either side of the web. Themanifolds direct continuous streams of pressurized fluid, such as air,outwardly toward the side edges of the web to smooth wrinkles in theweb. Additional manifolds are used to intermittently direct streams offluid to laterally move and guide the web.

U.S. Pat. No. 4,542,842 to Reba, entitled “Pneumatic conveying methodfor flexible webs,” discloses a method for conveying a web using innerand outer pairs of side jet nozzles employing the Coanda effect topropel the web while preventing undue distortion.

U.S. Pat. No. 5,979,731 to Long et al., entitled “Method and apparatusfor preventing creases in thin webs,” discloses an apparatus forremoving longitudinal wrinkles from a thin moving web of media. Themedia is wrapped around a perforated cylindrical air bar disposed inproximity to a contact roller.

U.S. Pat. No. 6,427,941 to Hikita, entitled “Web transporting method andapparatus,” discloses a web transporting apparatus that transports a webby floating the web on air jetted from holes formed in a roller whilethe edges of the web are supported by edge rollers.

There remains a need for a means to prevent the formation of receivermedia wrinkles as a receiver media contacts web-guiding structures in adigital printing system.

SUMMARY OF THE INVENTION

The present invention represents a web-guiding system for guiding a webof media travelling from upstream to downstream along a transport pathin an in-track direction, the web of media having a first side and anopposing second side, comprising:

a fixed web-guiding structure including:

-   -   a first fixed web-guiding structure section having a convex        exterior surface, wherein a pattern of air holes are formed        through the exterior surface; and    -   a second fixed web-guiding structure section having a convex        exterior surface, wherein a pattern of air holes are formed        through the exterior surface, wherein the exterior surface of        the second fixed web-guiding structure section is aligned with        the exterior surface of the first fixed web-guiding structure        section;

at least one air source for providing an air flow through the air holesin the first and second fixed web-guiding structure sections; and

a web-guiding roller located between the first and second fixedweb-guiding structure sections, the web-guiding roller being rotatablearound a roller axis;

wherein the web-guiding roller has a width in the direction of theroller axis which is less than 20% of a cross-track width of the web ofmedia;

wherein the web of media travels around the web-guiding roller and thefirst and second fixed web-guiding structure sections through a wrapangle of more than 10 degrees, with the web of media contacting anexterior surface of the web-guiding roller, and

wherein the air flow through the air holes lifts the web of media awayfrom the first and second web-guiding structure sections such that thefirst side of the web of media is substantially not in contact with thefirst and second web-guiding structure sections.

This invention has the advantage that the web of media can be redirectedaround the fixed web-guiding structure by a large wrap angle withoutforming wrinkles in the web of media.

It has the additional advantage that the web-guiding roller provides alateral constraint to prevent the web of media from drifting laterally.The narrow width of the web-guiding roller prevents the formation ofwrinkles as the web of media passes around the web-guiding roller.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the formation of flutes in a continuous web ofreceiver media due to cross-track expansion of the receiver media;

FIG. 2 is a simplified side view of an inkjet printing system;

FIG. 3 is a simplified side view of an inkjet printing system forprinting on both sides of a web of receiver media;

FIGS. 4A and 4B show schematic side-view diagrams illustratingweb-guiding systems including a fixed web-guiding structure and aweb-guiding roller in accordance with embodiments of the presentinvention;

FIG. 5 shows a schematic side-view diagram illustrating a web-guidingsystem which includes a fixed web-guiding structure and two web-guidingrollers in accordance with an alternate embodiment;

FIG. 6 is a perspective drawing showing the web-guiding system of FIG.5;

FIG. 7 shows a schematic side-view diagram illustrating a web-guidingsystem which includes a fixed web-guiding structure and two web-guidingrollers which are recessed into the fixed web-guiding structure inaccordance with an alternate embodiment;

FIG. 8 is a perspective drawing showing the web-guiding system of FIG.7;

FIGS. 9-10 are perspective drawings showing variations of theweb-guiding system of FIG. 8 incorporating narrow web-guiding rollers;

FIG. 11 is a perspective drawing showing a web-guiding system whereinthe fixed web-guiding structure is used to provide a turn-bar function;

FIG. 12 shows a schematic top-view diagram illustrating a web-guidingturn-bar system incorporating a plurality of web-guiding rollers inaccordance with an alternate embodiment;

FIG. 13 shows a schematic side-view diagram illustrating a web-guidingsystem which includes a web-guiding roller protruding through a fixedweb-guiding structure in accordance with an alternate embodiment;

FIG. 14 is a perspective drawing showing the web-guiding system of FIG.13;

FIG. 15 shows a schematic side-view diagram illustrating a web-guidingsystem which includes two fixed web-guiding structure sections on eitherside of a web-guiding roller in accordance with an alternate embodiment;

FIG. 16 is a perspective diagram illustrating a web-guiding system whichincludes a grooved web-guiding roller providing a Bernoulli force and afixed web-guiding structure in accordance with an alternate embodiment;

FIG. 17 is a schematic side-view diagram showing a portion of theweb-guiding system of FIG. 16; and

FIGS. 18-21 illustrate exemplary air flow control mechanisms that can beused to control the airflow through the air holes in the fixedweb-guiding structures.

DETAILED DESCRIPTION OF THE INVENTION

The present description will be directed in particular to elementsforming part of, or cooperating more directly with, an apparatus inaccordance with the present invention. It is to be understood thatelements not specifically shown, labeled, or described can take variousforms well known to those skilled in the art. In the followingdescription and drawings, identical reference numerals have been used,where possible, to designate identical elements. It is to be understoodthat elements and components can be referred to in singular or pluralform, as appropriate, without limiting the scope of the invention.

The invention is inclusive of combinations of the embodiments describedherein. References to “a particular embodiment” and the like refer tofeatures that are present in at least one embodiment of the invention.Separate references to “an embodiment” or “particular embodiments” orthe like do not necessarily refer to the same embodiment or embodiments;however, such embodiments are not mutually exclusive, unless soindicated or as are readily apparent to one of skill in the art. Itshould be noted that, unless otherwise explicitly noted or required bycontext, the word “or” is used in this disclosure in a non-exclusivesense.

The example embodiments of the present invention are illustratedschematically and may not be to scale for the sake of clarity. One ofordinary skill in the art will be able to readily determine the specificsize and interconnections of the elements of the example embodiments ofthe present invention.

As described herein, the exemplary embodiments of the present inventionprovide receiver media guiding components useful for guiding thereceiver media in inkjet printing systems. However, many otherapplications are emerging which use inkjet printheads to emit liquids(other than inks) that need to be finely metered and deposited with highspatial precision. Such liquids include inks, both water based andsolvent based, that include one or more dyes or pigments. These liquidsalso include various substrate coatings and treatments, variousmedicinal materials, and functional materials useful for forming, forexample, various circuitry components or structural components. As such,as described herein, the terms “liquid” and “ink” refer to any materialthat is ejected by the printhead or printhead components describedbelow.

Inkjet printing is commonly used for printing on paper, however, thereare numerous other materials in which inkjet is appropriate. Forexample, vinyl sheets, plastic sheets, textiles, paperboard andcorrugated cardboard can comprise the receiver media. Additionally,although the term inkjet is often used to describe the printing process,the term jetting is also appropriate wherever ink or other liquids isapplied in a consistent, metered fashion, particularly if the desiredresult is a thin layer or coating.

Inkjet printing is a non-contact application of an ink to a receivermedia. Typically, one of two types of ink jetting mechanisms is used,and is categorized by technology as either drop-on-demand inkjetprinting or continuous inkjet printing.

Drop-on-demand inkjet printing provides ink drops that impact upon arecording surface using a pressurization actuator, for example, athermal, piezoelectric or electrostatic actuator. One commonly practiceddrop-on-demand inkjet type uses thermal energy to eject ink drops from anozzle. A heater, located at or near the nozzle, heats the inksufficiently to form a vapor bubble that creates enough internalpressure to eject an ink drop. This form of inkjet is commonly termed“thermal inkjet.” A second commonly practiced drop-on-demand inkjet typeuses piezoelectric actuators to change the volume of an ink chamber toeject an ink drop.

The second technology commonly referred to as “continuous” inkjetprinting, uses a pressurized ink source to produce a continuous liquidjet stream of ink by forcing ink, under pressure, through a nozzle. Thestream of ink is perturbed using a drop forming mechanism such that theliquid jet breaks up into drops of ink in a predictable manner. Onecontinuous inkjet printing type uses thermal stimulation of the liquidjet with a heater to form drops that eventually become printing dropsand non-printing drops. Printing occurs by selectively deflecting eitherthe printing drops or the non-printing drops and catching thenon-printing drops using catchers. Various approaches for selectivelydeflecting drops have been developed including electrostatic deflection,air deflection, and thermal deflection.

There are typically two types of receiver media used with inkjetprinting systems. The first type of receiver media is in the form of acontinuous web, while the second type of receiver media is in the formof cut sheets. The continuous web of receiver media refers to acontinuous strip of receiver media, generally originating from a sourceroll. The continuous web of receiver media is moved relative to theinkjet printing system components using a web transport system, whichtypically include drive rollers, web guide rollers, and web tensionsensors. Cut sheets refer to individual sheets of receiver media thatare moved relative to the inkjet printing system components via rollersand drive wheels or via a conveyor belt system that is routed throughthe inkjet printing system.

The invention described herein is applicable to both drop-on-demand andcontinuous inkjet printing technologies that print on continuous webs ofreceiver media. As such, the term “printhead” as used herein is intendedto be generic and not specific to either technology. Additionally, theinvention described herein is also applicable to other types of printingsystems, such as offset printing and electrophotographic printing, thatprint on continuous webs of receiver media.

The terms “upstream” and “downstream” are terms of art referring torelative positions along the transport path of the receiver media;points on the receiver media move along the transport path from upstreamto downstream.

Referring to FIG. 2, there is shown a simplified side view of a portionof a digital printing system 100 for printing on a first side 15 of acontinuous web of receiver media 10. The printing system 100 includes aprinting module 50 which includes printheads 20 a, 20 b, 20 c, 20 d,dryers 40, and a quality control sensor 45. In this exemplary system,the first printhead 20 a jets cyan ink, the second printhead 20 b jetsmagenta ink, the third printhead 20 c jets yellow ink, and the fourthprinthead 20 d jets black ink.

Below each printhead 20 a, 20 b, 20 c, 20 d is a media guide assemblyincluding print line rollers 31 and 32 that guide the continuous web ofreceiver media 10 past a first print line 21 and a second print line 22as the receiver media 10 is advanced along a media path in the in-trackdirection 4. Below each dryer 40 is at least one dryer roller 41 forcontrolling the position of the web of receiver media 10 near the dryers40.

Receiver media 10 originates from a source roll 11 of unprinted receivermedia 10, and printed receiver media 10 is wound onto a take-up roll 12.Other details of the printing module 50 and the printing system 100 arenot shown in FIG. 2 for simplicity. For example, to the left of printingmodule 50, a first zone 51 (illustrated as a dashed line region inreceiver media 10) can include a slack loop, a web tensioning system, anedge guide and other elements that are not shown. To the right ofprinting module 50, a second zone 52 (illustrated as a dashed lineregion in receiver media 10) can include a turnover mechanism and asecond printing module similar to printing module 50 for printing on asecond side of the receiver media 10.

Referring to FIG. 3, there is shown a simplified side view of a portionof a printing system 110 for printing on both a first side 15 and asecond side 16 of a continuous web of receiver media 10. Printing system110 includes a first printing module 55, for printing on a first side 15of the continuous web, having two printheads 20 a, 20 b and a dryer 40;a turnover mechanism 60; and a second printing module 65, for printingon the second side of the continuous web, having two printheads 25 a and25 b and a dryer 40. A web-guiding system 30 guides the web of receivermedia 10 from upstream to downstream along a transport path in anin-track direction 4 past through the first printing module 55 and thesecond printing module 65. The web-guiding system 30 includes rollersaligned with the print lines of the printheads 20 a, 20 b, 25 a, and 25b. These rollers maintain the receiver media 10 at a fixed spacing fromthe printing modules to ensure a consistent time of flight for the printdrops emitted by the printheads. The web-guiding system 30 also includesa web-guiding structure 70, which can be a roller for example,positioned near the exit of first printing module 55 for redirecting adirection of travel of the web of receiver media 10 along exit direction9 in order to guide web of receiver media 10 toward the turnovermechanism 60. The movement of the receiver media of the guiding rollersof the web guide system also maintains the cross-track position of thecontinuous web provided there is sufficient traction between thecontinuous web and the guiding rollers.

It is not uncommon for a web-guiding system 30 to include a web-guidingstructure that provides a large angular change in the direction oftravel of the web of the receiver media 10. Such large angular changesmay be required by geometric constraints on the overall dimensions ofthe web-guiding system 30 or the need to align the web of receiver media10 with a downstream portion of the web-guiding system 30. For example,web-guiding structure 70, which is positioned near the exit of firstprinting module 55, redirects the direction of travel of the web ofreceiver media 10 by about 90° into exit direction 9 in order to guideweb of receiver media 10 toward the turnover mechanism 60.

When the receiver media 10 is a hygroexpansive material such ascellulose based paper, and at least portions of the receiver media 10are moistened such as by inkjet printing, the receiver media can beprone to wrinkling when wrapped at high wrap angles around a roller. Asimilar tendency to wrinkle exists at high wrap angle rollers when avery thin receiver media, such as plastic films of polyethylene andpoly(ethylene terephthalate), is being transported along the transportpath by the web-guiding system 30, as such receiver media 10 lack thecompressive strength to flatten the ripples produced in the receivermedia 10 by the variations in the in-track and cross-track tension.

FIG. 4A shows an embodiment of a web-guiding system 200 that overcomesthe shortcomings of prior art systems, allowing for high angular changesin the receiver media 10 without inducing the formation of wrinkles. Theweb-guiding system 200 includes a fixed web-guiding structure 205 havinga convex exterior surface 210. The web-guiding structure is fixed in thesense that it doesn't rotate or move with a surface speed thatcorresponds to the surface speed of the web of receiver media. The fixedweb-guiding structure 205 being “fixed” is not intended to indicate thatorientation of the fixed web-guiding structure 205 cannot be adjusted,either actively or passively, to align the fixed web-guiding structure205 relative to the transport path of the receiver media 10. In theillustrated embodiment first side 15 of the receiver media 10 faces theexterior surface 210 of the fixed web-guiding structure 205, whilesecond side 16 faces away from the fixed web-guiding structure 205.

A pattern of air holes 215 is formed through the exterior surface 210 ofthe fixed web-guiding structure 205, through which air 225 supplied byan air source 220 can flow. As the web of receiver media 10 travelsaround the fixed web-guiding structure 205, the flow of air 225 throughthe air holes 215 serves as an air bearing lifting the web of receivermedia 10 away from the fixed web-guiding structure 205 such that firstside 15 of the web of receiver media 10 is substantially not in contactwith the fixed web-guiding structure 205. Within the context of thepresent disclosure, “substantially not in contact” means that thereceiver media 10 contacts less than 5% of the exterior surface 210 ofthe fixed web-guiding structure 205 that is adjacent to the receivermedia 10. (The fixed web-guiding structure 205 is sometimes referred toin the art as an “air shoe” or an “air bearing structure.”)

As the web of receiver media 10 is supported by the air 225 so thatthere is minimal contact between the receiver media 10 and the exteriorsurface 210 of the fixed web-guiding structure 205, the receiver media10 has minimal friction with the fixed web-guiding structure 205. As aresult, the receiver media 10 can pass over the fixed web-guidingstructure 205 without scuffing the receiver media 10. Furthermore, thetransverse bending of the web of receiver media 10 as it goes around thefixed web-guiding structure 205 tends to flatten the web of receivermedia 10. The lack of angular constraint on the receiver media 10 allowsthe receiver media 10 to spread laterally to enable the flattening ofthe web. The fixed web-guiding structure 205 can therefore accommodatelarge wrap angles α_(s) of the receiver media 10 without wrinkling. Inthe illustrated embodiment, the wrap angle α_(s) is approximately 90degrees. Generally, the wrap angle α_(s) around the fixed web-guidingstructure 205 will be more than about 10 degrees, and it may be as largeas 180 degrees or more.

Because the receiver media 10 has minimal friction with the fixedweb-guiding structure 205, it provides little or no lateral constraintto impede the lateral (i.e., cross-track) movement of the web ofreceiver media 10. Therefore, while the low friction is beneficial forinhibiting the formation of wrinkles, it has the detrimental effect ofallowing the print media to drift in the cross-track direction 7 (FIG.1). To compensate for this, the web-guiding system 200 also includes aweb-guiding roller 230 having a roller axis 235 located along the mediapath in proximity to the fixed web-guiding structure 205. Theweb-guiding roller 230 provides a lateral constraint on the receivermedia 10 when it is placed in close proximity to the fixed web-guidingstructure 205 to inhibit cross-track drift or wander of the receivermedia 10. Within the context of the present disclosure, the term “inproximity” should be taken to mean that the distance D that the receivermedia 10 travels along the transport path between the web-guiding roller230 and the fixed web-guiding structure 205 is less than either twodiameters of the web-guiding roller 230 or 10% of the cross-track widthof the receiver media 10, whichever is larger.

In a preferred embodiment, the web-guiding roller 230 is located on thesame side of the web of receiver media 10 as the fixed web-guidingstructure 205 as illustrated in FIG. 4A so that the receiver media 10wraps around both elements in the same wrap direction (e.g., clockwisein FIG. 4A). In alternate embodiments (not shown) the web-guiding roller230 can be located on the opposite side of the web of receiver media 10as the fixed web-guiding structure 205. This alternate placement of theweb-guiding roller 230 may be preferred in applications where a justprinted side of the receiver media 10 is facing toward the fixedweb-guiding structure 205. Placement of the web-guiding roller 230 onthe opposite side of the receiver media 10 can reduce the risk ofsmearing or offsetting non-cured ink through contact with theweb-guiding roller 230. The air bearing nature of the fixed web-guidingstructure 205 prevents the smearing or offsetting non-cured ink as thereceiver media 10 travels over the fixed web-guiding structure 230.

In a preferred embodiment, the web-guiding roller 230 is locatedimmediately upstream of the fixed web-guiding structure 205 as is shownin FIG. 4A, but placement of the web-guiding roller 230 immediatelydownstream of the fixed web-guiding structure 205 as shown in theweb-guiding system 201 of FIG. 4B is also effective for inhibitingcross-track drift or wander of the receiver media 10. As the web-guidingroller 230 provides an angular constraint in addition to the lateralconstraint, the placement of the web-guiding roller 230 immediatelyupstream of the fixed web-guiding structure 205 has the advantage thatit reduces any lateral shifts in the receiver media 10 that might beproduced by an angular drift of the web at the entrance to the fixedweb-guiding structure 205.

As is taught in commonly-assigned U.S. Pat. No. 6,003,988 to McCann etal., entitled “Printer architecture,” which is incorporated herein byreference, the formation of creases or wrinkles in a web of mediatraveling through an inkjet printing system can be inhibited by limitingthe wrap of the receiver media around rollers to small wrap angles.Therefore, to avoid the formation of wrinkles in the web-guiding system200 of the present invention, the wrap angle α_(r) of the receiver media10 around the web-guiding roller 230 is preferably less than about fivedegrees.

FIGS. 5 and 6 show an alternate embodiment of a web-guiding system 202in which there are two web-guiding rollers 230, one immediately upstreamand one immediately downstream of the fixed web-guiding structure 205.The addition of the second web-guiding roller 230 immediately downstreamof the fixed web-guiding structure 205 further enhances the cross-trackstability of the web of receiver media 10. By limiting the wrap anglearound the upstream web-guiding roller 230 (α_(r1)) and the wrap anglearound the downstream web-guiding roller 230 (α_(r2)) of this embodimentto small wrap angles, such as less than about 5 degrees, the formationof creases or wrinkles around these web-guiding rollers 230 isinhibited.

The exemplary embodiment of FIG. 6 shows the air holes 215 as beingcircular in shape; however, this is not a requirement. In otherembodiments, the air holes 215 can have other shapes such as ellipses,squares, rectangles or extended slits. In this example, the pattern ofair holes 215 takes the form of a regular grid of air holes 215 having afixed spacings in the cross-track direction 7 and the in-track direction4. In other embodiments, the air holes 215 can be arranged in otherpatterns such as hexagonal grids, or can have non-uniform spacings. Forexample, in some embodiments it may be useful to space the air holes 215non-uniformly so as to provide a substantially constant lifting forceacross the exterior surface 210 of the fixed web-guiding structure 205.Those skilled in the art will understand that fluid dynamics modelingcan be used to determine an optimized pattern of spacings between theair holes 215 to provide the constant lifting force.

In some embodiments, the web-guiding system can also include atensioning mechanism to provide a force on the web-guiding roller 230 topush it toward and into contact with the web of receiver media 10. Thetensioning mechanism can take many different forms such as coil springs,leaf springs, torsion springs, flexure arms, air cylinders, andelectro-mechanical actuators. In FIG. 5, a tensioning mechanism 240associated with the upstream web-guiding roller 230 provides straightline motion of the web-guiding roller 230, while a tensioning mechanism245 associated with the downstream web-guiding roller 230 includes apivot arm support for the web-guiding roller 230, through which theforce is applied to the web-guiding roller 230 by the tensioningmechanism 245. To ensure consistent tracking of the web of receivermedia 10, the roller axis 235 of the web-guiding rollers 230 must remainsubstantially perpendicular to the direction of media travel (i.e.,in-track direction 4) at the location along the transport path where theweb of receiver media 10 contacts the web-guiding rollers.

In some embodiments, a roller control mechanism (not shown) is providedfor adjusting an orientation of the roller axis 235 relative to thein-track direction 4. This can be used to provide a steering force onthe web of receiver media 10. The roller control mechanism can include amedia edge sensor (not shown) which detects a position of the receivermedia 10 and adjusts the roller axis 235 to compensate for any driftfrom a nominal position.

FIGS. 7 and 8 show another embodiment of a web-guiding system 203 inwhich the web-guiding rollers 230 are integrated into fixed web-guidingstructure 205. This allows the web-guiding rollers 230 to be alignedwith the fixed web-guiding structure 205 with more precision. Thecontact of the web of receiver media 10 against the web-guiding rollers230 forms an air seal, preventing air 225 from passing between theweb-guiding rollers 230 and the web of receiver media 10. When theweb-guiding rollers 230 are recessed into the fixed web-guidingstructure 205 such that there is only a small gap between theweb-guiding roller 230 and the leading edge or the trailing edge of thefixed web-guiding structure 205, it blocks most of the air 225 fromescaping along the leading edge and the trailing edge of the fixedweb-guiding structure 205. By blocking the flow of air from along theleading and trailing edges of the fixed web-guiding structure 205, theintegration of the web-guiding rollers 230 into the fixed web-guidingstructure 205 can reduce the required flow rate for the air 225necessary to float the receiver media 10 over the surface of the fixedweb-guiding structure 205. Another advantage of providing air sealsalong the leading and trailing edges of the fixed web-guiding structure205 is that more of the air 225 must escape from the region between thefixed web-guiding structure 205 and the receiver media 10 by flowinglaterally (i.e., in a cross-track direction 7) as shown in FIG. 8. Thislateral flow of air 225 provides a lateral force on the web of receivermedia 10 which tends to spread the receiver media 10 in the cross-trackdirection 7, thereby further discouraging the formation of wrinklesPreferably, at least 80% of the air 225 exits the region between the webof receiver media 10 and the fixed web-guiding structure 205 in alateral direction. Therefore, it can be seen that the use of twoweb-guiding rollers 230 positioned immediately adjacent to the leadingand trailing edges of the fixed web-guiding structure 205 provides afurther enhancement in the spreading of the web of the receiver media 10when compared to the use of a single web-guiding roller 230 as in theembodiments of FIGS. 4A-4B, and also compared to the placement of theweb-guiding rollers 230 at a larger distance from the fixed web-guidingstructure 205 as shown in FIG. 5.

The web-guiding rollers 230 must be spaced away at least a small gapdistance away from the fixed web-guiding structure 205 to enable theweb-guiding rollers 230 to rotate freely. The gap 255 provides a leakagepath for air 225 to escape from out between the fixed web-guidingstructure 205 and the receiver media 10. It is desirable to limit theamount of air 225 that flows through the gap 255. In the embodimentshown in FIGS. 7-8, the gap 255 is configured to have an extendedlength, by partially recessing the web-guiding rollers 230 within thefixed web-guiding structure 205. Preferably, the web-guiding rollers 230are recessed within the fixed web-guiding structure 205 for at least 20%of their circumference. The extended length of the gap 255 providesimpedance to the flow of air 225 through the gap 255, thereby limitingthe leakage of air 225 through the gap 255. Preferably, the width of thegap is less than about 0.01 inches. In one exemplary embodiment, thewidth of the gap 255 is about 0.003 inches, and the gap 255 extendsaround about 35% of the circumference of the web-guiding roller 230. Theleakage of air 225 though the gap 255 can also be limited by using airseals 250 to further limit the flow of air 225 from escaping through thegap 255 between the fixed web-guiding structure 205 and the web-guidingrollers 230. In some embodiments, the air seals 250 can be fabricatedusing flexible sealing foil which provides a sliding seal across theexit of the gap 255. The use of air seals has the advantage that it canreduce the required flow rate for the air 225 necessary to float thereceiver media 10 over the surface of the fixed web-guiding structure205.

In some embodiments, an air conditioning subsystem 260 is included tocondition the air 225 before it exits the air holes 215 in the fixedweb-guiding structure 205. In the embodiment of FIGS. 7 and 8, the airconditioning subsystem 260 is located between the air source 220 and thefixed web-guiding structure 205. In alternative configurations, the airconditioning subsystem 260 can be positioned in other locations, such asinternal to the fixed web-guiding structure 205, internal to the airsource 220, or at an inlet to the air source 220. Depending on theapplication, the air conditioning subsystem 260 can be selected toperform various conditioning functions such as cooling the air, heatingthe air, altering the humidity of the air, or enriching or depleting theconcentration of particular gases that may react with, or be inert withrespect to, the ink or receiver media 10. Using the air conditioningsubsystem 260 in combination with the embodiments which use recessedweb-guiding rollers 230 to limit the air leakage in the upstream anddownstream directions has the advantage that it reduces the requiredflow rate of the air 225 that must be conditioned by the airconditioning subsystem 260.

In some embodiments, the web-guiding rollers 230 extend across theentire width of the receiver media 10 as shown in FIGS. 6 and 8. Inother embodiments, narrow web-guiding rollers 232 can be used, which arenarrow when compared to the width of the web of receiver media 10 asillustrated in the web-guiding system 204 of FIG. 9. For example, thewidth of the narrow web-guiding rollers 232 (in the direction of theroller axis 235) can be less than about 20% of the cross-track width ofthe web of receiver media 10.

The narrow web-guiding rollers 232, like the full-width web-guidingrollers 230 (FIG. 6), provide a lateral constraint to the web ofreceiver media 10 to prevent the cross-track drifting or wandering ofthe web of receiver media 10. The narrow web-guiding rollers 232 providea lateral constraint to that portion of the web of receiver media thatcontacts the narrow guiding roller. When the narrow web-guiding rollers232 are centrally located across the width of the web of receiver media10, they provide the lateral constraint to the center of the web, whilenot imposing a lateral constraint on the portions of the web which arespaced away from the center of the web. This has the advantage that itpermits the receiver media 10 to expand laterally away from thecenterline of the web when moistened, while preventing an overalllateral drift to the web of receiver media 10. As the receiver media 10can freely expand or contract in the cross track direction, the heightof any flutes that may be present can be reduced prior to reaching thefixed web-guiding structure 205.

FIG. 10 illustrates an embodiment of a web-guiding system 206 where theweb-guiding roller 230 downstream of the fixed web-guiding structure 205spans the entire width of the web of receiver media 10, while a narrowweb-guiding roller 232 is used upstream of the fixed web-guidingstructure 205. The upstream narrow web-guiding roller 232 preventslateral drifting of the web of receiver media 10 while allowing forlateral expansion or shrinkage of the receiver media 10 as in the FIG. 9embodiment. As the web of receiver media 10 wraps around the fixedweb-guiding structure 205, the receiver media 10 spreads laterally toflatten any flutes which may have initially been present. The use of awide web-guiding roller 230 downstream of the fixed web-guidingstructure 205 can inhibit the newly spread receiver media 10 fromcontracting laterally downstream of the fixed web-guiding structure 205.

As illustrated in FIG. 11, the principles of the present invention canalso be applied to turn-bar systems, which are used to turn over the webof receiver media 10. Turn-bar system 300 includes a fixed web-guidingturn-bar structure 305, together with a narrow web-guiding roller 232located in proximity to the fixed web-guiding turn-bar structure 305.The narrow web-guiding roller 232 is positioned so that it contacts thefirst side 15 of receiver media 10 upstream of the fixed web-guidingturn-bar structure 305.

The fixed web-guiding turn-bar structure 305 is oriented at an obliqueangle relative to the initial in-track direction 4 for the web ofreceiver media 10. In this example, the receiver media 10 is wrappedaround the convex exterior surface 310 of the fixed web-guiding turn-barstructure 305 for a wrap angle α_(s) of about 180°, and the fixedweb-guiding turn-bar structure 305 is angled by about 45 degreesrelative to the initial in-track direction 4 so that the receiver media10 exits the turn-bar system 300 with a new in-track direction 4′ and anew cross-track direction 7′, which are rotated approximately 90°relative to the input directions. As the receiver media 10 exits theturn-bar system 300, the receiver media 10 has been inverted so that thefirst side 15 is now on top, and the second side 16 is on the bottom.

In the illustrated embodiment, the convex exterior surface 310 of theexemplary fixed web-guiding turn-bar structure 305 has a semi-circularprofile. In other embodiments, the convex exterior surface 310 cansubtend a complete circle (e.g., to provide additional stiffness), orcan subtend an arc somewhere between 180° and 360°.

The fixed web-guiding turn-bar structure 305 includes a pattern of airholes 215 formed in the exterior surface 310 through which air 225 fromair source 220 flows to lift the web of receiver media 10 away from thefixed web-guiding turn-bar structure 305 such that the first side 15 ofthe web of receiver media 10 is substantially not in contact with theexterior surface 310. Preferably the air holes 215 are positioned onlyin those portions of the exterior surface 310 over which are covered bythe receiver media 10.

The narrow web-guiding roller 232 is oriented such that the roller axis235 is substantially perpendicular to the in-track direction 4 in whichthe receiver media 10 is travelling upstream of the fixed web-guidingturn-bar structure 305. Preferably, the narrow web-guiding roller 232 ispositioned so that it contacts the web of receiver media 10 near thecenterline of the web. The lateral constraint provided to the web ofreceiver media 10 by the narrow web-guiding roller 232 reduces thetendency of the web to drift laterally in response to tension changes asthe web wraps around the angled fixed web-guiding turn-bar structure305. The use of a narrow web-guiding roller 232 enables the lateralconstraint to be applied to the web in closer proximity to the fixedweb-guiding turn-bar structure 305 than would be possible with a wideweb-guiding roller 230 (FIG. 6).

FIG. 12 shows a top-view of another embodiment of a turn-bar system 301in which there are a plurality of narrow web-guiding rollers 232 locatedat different lateral locations across the web of receiver media 10upstream of the fixed web-guiding turn-bar structure 305. (Note that theair source 220 is not shown in this figure for clarity.) The narrowweb-guiding rollers 232 are positioned so that they contact the firstside 15 of receiver media 10. The use of multiple narrow web-guidingrollers 232 in this embodiment can further reduce the tendency of theweb of receiver media 10 to wander relative to the embodiment shown inFIG. 11 which uses only a single narrow web-guiding roller 232.

FIG. 12 also shows an additional narrow web-guiding roller 332positioned downstream of the fixed web-guiding turn-bar structure 305.The narrow web-guiding roller 232 is positioned so that it contacts thefirst side 15 of receiver media 10 downstream of the fixed web-guidingturn-bar structure 305 to provide a lateral constraint to the web ofreceiver media 10 as it leaves the turn-bar system 301. The roller axis235 of the narrow web-guiding roller 332 is oriented so that it issubstantially perpendicular to the new in-track direction 4′.

FIGS. 13-14 illustrate another embodiment of a web-guiding system 207 inwhich the narrow web-guiding roller 232 is positioned so that itprotrudes through the exterior surface 210 of the fixed web-guidingstructure 205 by a small height h. The height h that the narrowweb-guiding roller 232 protrudes through the exterior surface 210 ischosen such that it contacts the receiver media 10 through a wrap angleα_(r) that provides sufficient traction to impose a lateral constrainton the receiver media 10. The optimal height h will depend on thethickness of the air cushion around the fixed web-guiding structure 205.In a preferred embodiment, the contact angle α_(r) is less than about5-10°, and the height h is between 0.1 mm and 4 mm. In some embodiments,a tensioning mechanism (e.g., a spring, a flexure arm, an air cylinder,or an electro-mechanical actuator) can be used to push the web-guidingroller 232 into contact with the receiver media 10, therebyautomatically adjusting the height h to accommodate variations in thethickness of the air cushion around the fixed web-guiding structure 205.

FIG. 15 shows another embodiment of a web-guiding system 400 in whichthe web of receiver media 10 travels around the fixed web-guidingstructure 205 with air 225 flowing through the air holes 215 and liftingthe web of receiver media away from the fixed web-guiding structure 205such that the first side 15 of the web of receiver media 10 issubstantially not in contact with the fixed web-guiding structure 205.In this configuration, the fixed web-guiding structure 205 has two fixedweb-guiding structure sections 405, 406 which are located on each sideof an integrated, centrally-located narrow web-guiding roller 432. Theconvex exterior surface 210 of the fixed web-guiding structure 205 hasan arc-shaped profile with a radius of curvature r_(s) and a center ofcurvature 410 which is aligned with the roller axis 235 of the narrowweb-guiding roller 432. The narrow web-guiding roller 432 has a radiusof curvature that is slightly larger than the radius of curvature r_(s)of the fixed web-guiding structure 205 so that it protrudes through theexterior surface 210 of the fixed web-guiding structure 205 by a heighth. The optimal height h will depend on the thickness of the air cushionaround the fixed web-guiding structure 205. In a preferred embodiment,the height h is between 0.1 mm and 4 mm. Because the receiver media 10is substantially not in contact with the two fixed web-guiding structuresections 405, 406, the receiver media can wrap around the fixedweb-guiding structure 205 without risk of wrinkling. In someembodiments, a tensioning mechanism (e.g., a spring, a flexure arm, anair cylinder, or an electro-mechanical actuator) can be used to push thenarrow web-guiding roller 432 into contact with the receiver media 10,thereby automatically adjusting the height h to accommodate variationsin the thickness of the air cushion around the fixed web-guidingstructure 205.

The centrally-located narrow web-guiding roller 432 provides a lateralconstraint to the web of receiver media 10 to prevent lateral driftingof the web. The central location of the narrow web-guiding roller 432between the two fixed web-guiding structure sections 405, 406 allows thereceiver media 10 to expand and contract in the cross-track direction toaccommodate cross-track dimensional changes in the receiver media 10.This provides a distinct advantage when compared to the aforementionedU.S. Pat. No. 6,427,941, where cross-track width changes in the receivermedia are inhibited due to the placement of web-contacting edge rollerson both side of a central air bearing structure.

In the FIG. 15 embodiment, the wrap angle around the narrow web-guidingroller 432 is substantially equivalent to the wrap angle α_(s) aroundthe fixed web-guiding structure 205, and is therefore relatively large.However, because the narrow web-guiding roller 432 has a small lateralwidth, there is little risk that the receiver media 10 passing over thenarrow web-guiding roller 432 will form a wrinkle even if a flute wereto be aligned with the narrow web-guiding roller 432.

FIGS. 16 and 17 show a web-guiding system 500 according to an alternateembodiment which uses the approach described in commonly assigned,co-pending U.S. patent application Ser. No. ______ (Docket K001680),entitled “Media guiding system using Bernoulli force roller,” by Muir etal., which is incorporated herein by reference, to provide an enhancedtraction between the receiver media 10 and grooved web-guiding roller530. The fixed web-guiding structure 205 and air source 220 function inthe same manner as has been described earlier with respect to FIG. 4A sothat air 225 flowing through a pattern of air holes 215 lift the web ofreceiver media 10 away from the exterior surface 210 of the fixedweb-guiding structure 205.

The grooved web-guiding roller 530 is positioned in proximity to thefixed web-guiding structure 205, and includes at least one groove 535formed in around its exterior surface 540. A roller air source 520directs an airflow 525 into the groove 535, the air flow being directedbetween the first side 15 of the receiver media 10 and the exteriorsurface 540 of the grooved web-guiding roller 530. In a preferredembodiment, the airflow 525 is substantially parallel to the plane ofthe receiver media 10 (i.e., a vector representing the direction ofairflow 525 is within about 10° of being parallel to the in-trackdirection 4 of the receiver media 10) and to the groove 535 (i.e., avector representing the direction of airflow 525 is within about 10° ofbeing parallel to a plane through the center of the groove 535, wherethe plane through the center of the groove 535 will generally beperpendicular to the roller axis 235.)

As is described in more detail in the aforementioned U.S. patentapplication by Muir et al., the use of the grooved web-guiding roller530 and the airflow 525 provided by the roller air source 520 produce aBernoulli force F that draws the receiver media 10 down onto the groovedweb-guiding roller 530, thereby providing an increased traction. Thegroove 535 serves as an air channel for the airflow 525. As shown inFIG. 17, as the airflow 525 passes through the groove 535 between thefirst side 15 of receiver media 10 and the exterior surface 540 of thegrooved web-guiding roller 530, the contour of the bottom of the groove535 forms a constriction 545 to the airflow 525. The well-known“continuity principle” of fluid dynamics requires the airflow 525 toaccelerate as it passes through the constriction 545. According to thewell-known Bernoulli's Principle, the increased velocity of the airflow525 at the constriction 545 is accompanied by the development of a lowpressure zone between the high point of the groove 535 and the receivermedia 10. A pressure differential is therefore developed from the secondside 16 to the first side 15 of the receiver media 10, resulting in aBernoulli force F on the receiver media 10 which draws the receivermedia 10 down toward, or into contact with, the exterior surface 540 ofthe grooved web-guiding roller 530. This increases the wrap angle α_(r),and thereby increases the traction between the receiver media 10 and thegrooved web-guiding roller 530. As a result, the ability of the groovedweb-guiding roller 530 to provide a lateral constraint on the web ofreceiver media 10 is improved, thereby preventing the receiver media 10from drifting in the cross-track direction 7 (FIG. 16).

While FIGS. 16-17 illustrate the use of a narrow grooved web-guidingroller 530 located upstream of the fixed web-guiding structure 205, itwill be obvious to those skilled in the art that the same approach canbe used to provide extra traction for any of the rollers shown in FIGS.4A-15. In some embodiments a plurality of grooves 535 can be providedacross the width of the roller. This is particularly appropriate for thewider web-guiding rollers 230 such as those shown in FIG. 6.

In other alternate embodiments (not shown), different methods can beused to increase the traction between the receiver media 10 and thegrooved web-guiding roller 530. For example a jet of air directed ontothe second side 16 of the receiver media 10 can be used to push thereceiver media 10 down onto the web-guiding roller 230 (FIG. 4A).Alternately, an electrostatic force can be used to draw the receivermedia 10 down onto the web-guiding roller 230.

In some embodiments, the fixed web-guiding structure 205 include an airflow control mechanism for controlling which air holes 215 the flow ofair 225 is provided through. This allows the airflow width to beadjusted in accordance with the width of the web of receiver media 10 sothat doesn't flow through air holes 215 that are outside the width ofthe receiver media 10. FIGS. 18-21 show several exemplary embodiments ofair flow control mechanisms that can be used in accordance with thepresent invention.

FIG. 18 shows a view of the exterior surface 210 of a fixed web-guidingstructure 205 which is segmented into a left segment 265, a centersegment 266, and a right segment 267. The segments are separated byinternal walls 270 which are inside of the fixed web-guiding structure205 and define a plurality of air chambers corresponding to the leftsegment 265, the center segment 266, and the right segment 267. Thewalls are positioned such that the width of the center segment 266corresponds to the width of a narrow receiver media 10, and the totalwidth of the three segments corresponds to the width of a wide receivermedia 10. The air source 220 (FIG. 4A) provides airflow into the fixedweb-guiding structure 205 through separate air supply lines (not shown)into three different air supply ports 275, one for each segment. Valvesin the air supply lines can be used to turn on and off the airflow tothe individual segments to accommodate different receiver media widths.This approach can easily be extended to more than three segments toaccommodate additional media widths.

FIG. 19 shows another embodiment in which the air flow control mechanismcomprises moveable internal walls 271 within the fixed web-guidingstructure 205 that can be moved to adjust the size of an internal airchamber behind the air holes 215 within to an active segment 268 inorder to accommodate different media widths. Any mechanism known in theart can be used to adjust the position of the moveable internal walls271. In the illustrated embodiment, a motorized pinion gear 272 engagesrack gears 273 attached to each moveable internal wall 271 to adjust theposition of the end walls. Air flows into the fixed web-guidingstructure 205 through a central air supply port 275 located between themoveable internal walls 271 so that airflow is only provided in thecentral active segment 268.

FIGS. 20-21 illustrate another embodiment of an air flow controlmechanism which utilizes a moveable louver 280 located inside the fixedweb-guiding structure 205, adjacent to the interior side of the exteriorsurface 210. The louver 280 has a large central louver opening 281corresponding to the center segment 266 of the fixed web-guidingstructure 205 through which air can flow to pass through the air holes215. In the portions of the louver 280 corresponding to the left segment265 and the right segment 267, an array of linear louver openings 282are provided, having the same pitch in the cross-track direction 7 asthe air holes 215. The moveable louver 280 can be moved laterally to aposition where the array of louver openings 282 in the left segment 265and the right segment 267 are either aligned with the air holes 215 sothat air can pass (as in FIG. 20), or are blocking the air holes 215 sothat air cannot pass (as in FIG. 21). When the louver 280 is shifted tothe FIG. 20 position, air flows out of the air holes 215 across theentire width of the fixed web-guiding structure to support a wide mediawidth. When the louver 280 is shifted to the FIG. 21 position, air onlyflows out of the air holes 215 in the center segment 266 of the fixedweb-guiding structure to support a narrow media width. While theillustrated louver 280 supports two media widths, it will be obvious toone skilled in the art that other louver patterns can be used canaccommodate three or more media widths.

The invention has been described in detail with particular reference tocertain preferred embodiments thereof, but it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invention.

PARTS LIST

-   2 roller-   3 receiver media-   4 in-track direction-   4′ new in-track direction-   5 flute-   7 cross-track direction-   7′ new cross-track direction-   8 contact surface-   9 exit direction-   10 receiver media-   11 source roll-   12 take-up roll-   15 first side-   16 second side-   20 a printhead-   20 b printhead-   20 c printhead-   20 d printhead-   21 print line-   22 print line-   25 a printhead-   25 b printhead-   30 web-guiding system-   31 print line roller-   32 print line roller-   40 dryer-   41 dryer roller-   45 quality control sensor-   50 printing module-   51 first zone-   52 second zone-   55 printing module-   60 turnover mechanism-   65 printing module-   70 web-guiding structure-   100 printing system-   110 printing system-   200 web-guiding system-   201 web-guiding system-   202 web-guiding system-   203 web-guiding system-   204 web-guiding system-   205 fixed web-guiding structure-   206 web-guiding system-   207 web-guiding system-   210 exterior surface-   215 air holes-   220 air source-   225 air-   230 web-guiding roller-   232 narrow web-guiding roller-   235 roller axis-   240 tensioning mechanism-   245 tensioning mechanism-   250 air seal-   255 gap-   260 air conditioning subsystem-   265 left segment-   266 center segment-   267 right segment-   268 active segment-   270 internal wall-   271 moveable internal wall-   272 pinion gear-   273 rack gear-   275 air supply port-   280 louver-   281 central louver opening-   282 louver opening-   300 turn-bar system-   301 turn-bar system-   305 fixed web-guiding turn-bar structure-   310 exterior surface-   332 narrow web-guiding roller-   400 web-guiding system-   405 fixed web-guiding structure section-   406 fixed web-guiding structure section-   410 center of curvature-   432 narrow web-guiding roller-   500 web-guiding system-   520 roller air source-   525 airflow-   530 grooved web-guiding roller-   535 groove-   540 exterior surface-   545 constriction-   F Bernoulli force-   h height-   r_(s) radius of curvature-   α_(s) wrap angle-   α_(r) wrap angle-   α_(r1) wrap angle-   α_(r2) wrap angle

1. A web-guiding system for guiding a web of media travelling from upstream to downstream along a transport path in an in-track direction, the web of media having a first side and an opposing second side, comprising: a fixed web-guiding structure including: a first fixed web-guiding structure section having a convex exterior surface, wherein a pattern of air holes are formed through the exterior surface; and a second fixed web-guiding structure section having a convex exterior surface, wherein a pattern of air holes are formed through the exterior surface, wherein the exterior surface of the second fixed web-guiding structure section is aligned with the exterior surface of the first fixed web-guiding structure section; at least one air source for providing an air flow through the air holes in the first and second fixed web-guiding structure sections; and a web-guiding roller located between the first and second fixed web-guiding structure sections, the web-guiding roller being rotatable around a roller axis; wherein the web-guiding roller has a width in the direction of the roller axis which is less than 20% of a cross-track width of the web of media; wherein the web of media travels around the web-guiding roller and the first and second fixed web-guiding structure sections through a wrap angle of more than 10 degrees, with the web of media contacting an exterior surface of the web-guiding roller, and wherein the air flow through the air holes lifts the web of media away from the first and second web-guiding structure sections such that the first side of the web of media is substantially not in contact with the first and second web-guiding structure sections.
 2. The web-guiding system of claim 1 wherein the web-guiding roller includes one or more grooves formed around the exterior surface of the web-guiding roller.
 3. The web-guiding system of claim 1 wherein the web-guiding roller is mounted to the fixed web-guiding structure.
 4. The web-guiding system of claim 1 further including an air flow control mechanism for controlling which air holes the air flow is provided through in accordance with a width of the web of media.
 5. The web-guiding system of claim 4 wherein the air flow control mechanism includes one or more fixed walls internal to the fixed web-guiding structure which define a plurality of air chambers with independently controllable air supplies.
 6. The web-guiding system of claim 4 wherein the air flow control mechanism includes one or more moveable walls internal to the fixed web-guiding structure which define an internal air chamber corresponding to the air holes through which the air flow is provided.
 7. The web-guiding system of claim 4 wherein the air flow control mechanism includes one or more louvers positioned internal to the fixed web-guiding structure which are repositionable to cover different sets of air holes, thereby blocking air flow through the covered air holes.
 8. The web-guiding system of claim 1 further including an air conditioning subsystem to condition the air provided by the air source.
 9. The web-guiding system of claim 1 wherein the exterior surfaces of the first and second fixed web-guiding structure sections have an arc-shaped profile with a first center of curvature and a first radius of curvature, and the web-guiding roller has a second radius of curvature which is larger than the first radius of curvature, the roller axis of the web-guiding roller being aligned with the center of curvature of the first and second fixed web-guiding structure.
 10. The web-guiding system of claim 9 wherein the second radius of curvature exceeds the first radius of curvature by between 0.1 mm to 4 mm.
 11. The web-guiding system of claim 1 wherein the exterior surface of the web-guiding roller protrudes above the exterior surface of the first and second fixed web-guiding structure sections by a protrusion height.
 12. The web-guiding system of claim 11 wherein the protrusion height is between 0.1 mm to 4 mm.
 13. The web-guiding system of claim 1 wherein cross-track widths of the first and second fixed web-guiding structure sections are substantially equal so that the web-guiding roller is centrally-located in the fixed web-guiding structure in a cross-track direction.
 14. The web-guiding system of claim 1 further including a tensioning mechanism that provides a force on the web-guiding roller to push it toward the web of media. 